Final answer:
The unusual symptoms observed in young gay men in major cities, including New York, led to the identification of HIV/AIDS. The high number of orders for the drug pentamidine indicated the prevalence of AIDS-related symptoms in New York.
Step-by-step explanation:
In the early 1980s, doctors noticed a trend of young gay men in major cities, including New York, being diagnosed with a rare cancer called Kaposi's sarcoma. They also observed other symptoms, such as a rare form of pneumonia. These observations led to the identification of a new disease, initially known as Gay Related Immune Deficiency (GRID) but later renamed Human Immunodeficiency Virus/Autoimmune Deficiency Syndrome (HIV/AIDS).
The unusually high number of orders for the drug pentamidine in New York indicated that many people were experiencing symptoms related to HIV/AIDS, such as Kaposi's sarcoma and the rare pneumonia. These symptoms were prevalent among gay men and intravenous drug users, leading to the identification of HIV/AIDS as a blood-borne and sexually transmitted disease.